Cap maximum open database connections

Fixes Gitea opening too many connections, which can impact other apps
trying to connect as well.

site-cookbooks/kosmos_gitea/templates/default/app.ini.erb

@@ -24,6 +24,7 @@ NAME    = gitea
 USER    = gitea
 PASSWD  = <%= @postgresql_password %>
 SSL_MODE = disable
+MAX_OPEN_CONNS = 20
 
 [repository]
 ROOT = <%= @repository_root_directory %>